The present invention generally relates to a photo-mask and more particularly, to a method of manufacturing a photo-mask to be employed for a pattern exposure process (lithography) in a production line of an optical disc, and a photo-mask produced by said manufacturing method.
Commonly, a photo-mask has been employed for the formation of a pattern on an optical disc by a light exposure system. The conventional manufacturing process for such a photo-mask generally includes manufacturing steps as shown, for example, in FIGS. 14(a) to 14(e).
More specifically, at a step in FIG. 14(a), a non-light transmitting film 2 of Cr or the like is formed on a mask substrate 1 by vapor deposition, sputtering, etc., and then, at a step in FIG. 14(b), a resist film 3 is applied onto said thin film 2. Thereafter, by subjecting said resist film 3 to exposure and development, a resist pattern 4 is formed (FIG. 14(c)). Subsequently, the thin film 2 is subjected to etching (FIG. 14(d)), and finally, the resist film 3 is removed, thereby to form the photo-mask having a mask pattern 5 (FIG. 14(e)).
The photo-mask manufactured by the conventional method as described above, however, has such a disadvantage that various faults tend to be formed therein, since separation of the mask pattern takes place in a cleaning process and the like. Furthermore, owing to the recent tendency toward recording at a higher density, the mask-pattern has been required to be finer, and thus, it has become necessary to solve the defect in the conventional method as referred to above.